I'm planning to make my version of "color organ". http://neuroelec.com/2011/03/fft-library-for-arduino/I tried couple of FFT code for Arduino and found ELM Chan's works best for me. It seems accurate and faster than others.So I just more less package the library. All credit should go where it belongs.

Original Fixed point FFT library is from ELM Chan, http://elm-chan.org/works/akilcd/report_e.htmlA way to port it to the Arduino library and most demo codes are from AMurchick http://arduino.cc/forum/index.php/topic,37751.0.htmlProcessing app is based on codes from boolscott http://boolscott.wordpress.com/2010/02/04/arduino-processing-analogue-bar-graph-2/

Sounds like a great idea. I'm just starting out working with the Arduino and am using this FFT library as well.

For anyone having trouble getting this to compile due to the Assembly file or any other problems, just extract the 'ffft' folder from ffft_Library.zip to <Arduino_Dir>/libraries/. Run the Arduino IDE and click File -> Examples -> ffft -> Examples -> visualizer. Either compile or upload to test the files out.